Arik Armstead’s second season is done after he aggravated a season-long shoulder injury Sunday in the 49ers’ seventh straight defeat.

Armstead, a 2015 first-round draft pick, went on injured reserve Tuesday afternoon. His roster spot went to another defensive tackle, Chris Jones, who got claimed off waivers from the Miami Dolphins.

When training camp opened, Armstead looked poised for a breakout season in his first full-time role. But a week into camp, he hurt his left shoulder, and although he played through the injury for eight games, he aggravated the injury Sunday while reaching for a ballcarrier on the fourth snap of a 41-23 loss to New Orleans.

After going through individual conditioning Tuesday with the training staff, Armstead declined to detail his health and instead said: “You’ll now soon enough.” Two hours later, he was on injured reserve. The 6-foot-7 defensive tackle started the past four games and he finished the season with 21 tackles, 2 1/2 sacks and a forced fumble.

The 49ers’ league-worst defense could revert to the same three-linemen front they started the first four games: DeForest Buckner on the left side, Mike Purcell at nose tackle and Quinton Dial on the right side. Glenn Dorsey, if his reconstructed knee cooperates, is the more likely option to start at nose tackle ahead of Purcell, who was inactive last game.

Jones (6-1, 293 pounds) played the previous three seasons with the New England Patriots and the first seven games this season with the Miami Dolphins, who released him Monday. He had seven tackles this season for the Dolphins. With the Patriots, he totaled nine sacks, plus one more while starting 2 of 4 playoff games. Jones was a 2013 sixth-round draft pick by the Houston Texans.

Jimmie Ward gave up three touchdown catches to Brandon Marshall as the 49ers blew a lead in their Levi’s Stadium debut in 2014, and Sunday offers Ward a chance at revenge when Marshall and the Jets visit